Process for preparing metallocene procatalysts

Abstract

A process for producing metallocene procatalysts useful in a catalyst system for the polymerization of olefins, particularly to make stereospecific polymers, and more particularly polymerization to make isotactic polypropylene in which the product of a reaction between a suitable ligand and an alkali-alkyl is reacted with a transition metal salt in the presence of an accelerant that has at least one lone pair of electrons in its outer valence shell. When the metallocene procatalyst produced is used in a catalyst system for the production of isotactic polymers, specifically isotactic polypropylene, the metallocene procatalyst can be used without isolating and separating the racemic modification from the meso form.

What is claimed is: 
     
       1. A process comprising: reacting (a) the reaction product of a ligand selected from the group consisting of cyclopentadienyl, fluorenyl or indenyl and combinations thereof with an alkyl compound containing an alkali metal; with (b) a transition metal salt in the presence of (c) an accelerant having at least one lone pair of electrons in the outer valence shell, but not a labile proton, wherein the quantity of accelerant employed is less than about 70% by weight of the combined mass of the reaction product (a) and the transition metal salt (b) to form a metal compound. 
     
     
       2. The process according to claim 1, wherein the accelerant is selected from the group consisting of ethers, tertiary phosphines, tertiary amines, and pyridine. 
     
     
       3. The process according to claim 1, wherein the accelerant is selected from the group consisting of diethylether and tetrahydrofuran. 
     
     
       4. The process according to claim 1, wherein the quantity of accelerant is employed at between about 40% and about 55% of the combined mass of the solid reaction product and the transition metal salt. 
     
     
       5. The process according to claim 1, wherein the metallocene exists as both a racemic modification and a meso form. 
     
     
       6. The process according to claim 3, wherein the ligand is selected such that the metal compound has both a racemic modification and a meso form. 
     
     
       7. The process according to claim 3, wherein the ligand is a bridged bis(indenyl) compound. 
     
     
       8. The process of claim 1, wherein the reaction between the reaction product and transition metal salt in the presence of an accelerant is conducted in a non-polar solvent system and the accelerant is present at less than about 20% by weight. 
     
     
       9. The process according to claim 8, wherein the non-polar solvent is selected from the group of substituted and non-substituted hydrocarbons consisting of waxes, mineral oils, benzene, toluene, alkanes, and alkenes. 
     
     
       10. A process according to claim 1 wherein the metal compound is a metallocene of (L) y  R 1   z  (L')MX.sub.(x-y-1) wherein M is a metal selected from the group consisting of IIIB to VIII or a rare earth metal; L and L' are the same or different and are π-bonded ligands coordinated to M selected from the group consisting of cyclopentyl, indenyl, or fluorenyl groups which may be substituted with one or more hydrocarbyl groups containing 1 to 20 carbon atoms, R 1  is selected from the group consisting of C 1  -C 4  substituted or unsubstituted alkylene radicals, dialkyl or diaryl germanium or silicon groups, and alkyl or aryl phosphine or amine radicals bridging L and L'; each X is independently hydrogen, an aryl, alkyl, alkenyl, alkylaryl, or arylalkyl radical having 1-20 carbon atoms, a hydrocarboxy radical having 1-20 carbon atoms, a halogen, R 2  CO 2  --, or R 2   2  NCO 2  --, wherein each R 2  is a hydrocarbyl group containing 1 to about 20 carbon atoms; y is 0, 1, or 2; x is 1, 2, 3, or 4 depending upon the valence state of M; z is 0 or 1 and is 0 when y is 0; and x-y≧1. 
     
     
       11. A process according to claim 10 wherein the metallocene has a racemic and meso form. 
     
     
       12. A process according to claim 10 wherein M is Zr, L and L' are indenyls, z=1, and X is chloride or methyl. 
     
     
       13. A process according to claim 1 where the two ligands, L and L', are bridged by a C 1  -C 4  alkylene radical, dialkyl or diaryl germanium or silicon groups, or an alkyl or aryl phosphine or amine radical. 
     
     
       14. A process according to claim 1 wherein the reaction takes place in the additional presence of a non-polar solvent, such that the accelerant (c) is present at greater than 0% and less than about 20% by weight of the combined mass of the reaction product (a), transition metal salt (b) and non-polar solvent. 
     
     
       15. A process according to claim 14 wherein the accelerant is present at about 2% to about 10% by weight. 
     
     
       16. A process according to claim 1 wherein the ligand is substituted with one or more hydrocarbyl groups containing 1 to 20 carbon atoms. 
     
     
       17. A process according to claim 1 where there are two ligands which are bridged by a C 1  -C 4  alkylene radical, dialkyl or diaryl germanium or silicon groups, or an alkyl or aryl phosphine or amine radical.